Hydrocarbons are susceptible to chemical reactions due to aging, heat and oxidation. One effect of oxidation, for example, is to produce soluble and insoluble materials of higher molecular weight and boiling point than the original hydrocarbon. These materials can have deleterious effects on the ultimate use of the hydrocarbons.
In particular, turbine combustion fuel oils, such as JP-4, JP-5, JP-7, JP-8, Jet A, Jet A-1, and Jet B are subject to harsh conditions. Fuel burned in an aircraft engine is often used as a cooling medium or heat sink to cool aircraft subsystems and engine lubricating systems prior to its combustion. As the fuel passes through the heat exchangers, it is subjected to temperature increases of several hundred degrees in a matter of seconds. Any unstable constituents in the fuel will quickly react under these severe conditions forming gums, varnishes and coke deposits. These deposits will plug-up the components leading to operational problems including reduced thrust and performance anomalies.
Treatment of these problems in hydrocarbons has often been accomplished with additives such as antioxidants, metal deactivators and corrosion inhibitors. Surfactants in the form of dispersants are often added to assist in retarding fouling of the hydrocarbons. However, hydrocarbons contain a number of naturally occurring dispersants as well as those of the additive variety. Consequently, this makes analytical determination of any one dispersant present in the hydrocarbon difficult due to contributions from the other dispersants present. The present inventors have surprisingly discovered an analytical method for determining the concentration of selected dispersants in transparent hydrocarbon fuel that avoids interferences from other dispersants present in the hydrocarbon.
Analytical tests based on turbidity measurement are often encountered in clinical chemistry and molecular biology laboratories. In these tests, turbidity measurement is used as a means of detecting and quantifying the concentration of a species which is made to precipitate from solution or absorb onto dispersed latex particles. A related analytical method utilizes turbidity measurements to detect suspended solids. Nephelometry is a photometric analytical technique for measuring the light scattered by finely divided particles of a substance in suspension. These techniques are used in industries as diverse as brewing and smart appliance manufacture (e.g., washing machines). The focus application of the turbidity measurement in these examples is to quantitate the solids present in the fluid, not to quantitate the concentration of dispersant in the fluid. However, none of these techniques account for methods to counteract the interference of other dispersants in the tested fluids.